Polar M400 Review

I was initially very disappointed with the Polar M400, but over time I've come to appreciate the M400 more and more. There are a number of factors, not least of which is that it now sells for far less than its release price, making it a lot more competitive. Its GPS Accuracy has also improved, though it still mediocre. This accuracy problem is offset by its reasonable support for the Stryd Footpod that is extremely accurate. The main competition the M400 faces is the Garmin Vivoactive. The Vivoactive is a better watch in virtually every respect, except for its Stryd support. In order to get the Vivoactive to get pace and distance information from Stryd you have to turn off GPS, while the M400 can use Stryd for pace and distance whilst still recording a GPS track.

How far did I run? This is the most basic question, and the M400 has poor GPS accuracy, but this can be offset by using the Stryd Footpod. It may seem odd to spend more on a Footpod than the watch, but I'd argue this is actually a reasonable compromise.

How fast am I running? Knowing how fast you're running can be a nice to know, or it can be vital for your training or race performance. Because of the nature of GPS, watches that rely on GPS signal alone tend to have serious problems with current pace. With the Stryd Footpod, you can get extremely accurate pace information, but without it, the M400 is pretty hopeless.

Where am I? The M400 has only a simple "back to start" arrow, which is better than nothing, but remember this is an "as the crow flies" direct path, not a backtrack.

What's my cadence? Cadenceis one of the most critical and often overlooked aspects of running. If you get your Cadence right, many other things naturally fall into place. The M400 has support for other Footpods besides Stryd, plus it has support for Cadence from the internal accelerometer. There are no Cadence alerts which is a shame, but typically this feature is only available on more expensive devices.

The M400 is not a good choice for ultrarunners, as its battery life is too short. See Watches for Ultrarunning for more details.

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1 Should You Buy The M400?

I think that in most cases, at this price point you should buy the Garmin Vivoactive over the M400. The Vivoactive has far more functionality than the M400, including Connect IQ that allows for expanded functionality through downloaded apps. The Vivoactive is a vastly better activity tracker, especially when combined with a good Connect IQ watch face that gives you better feedback on how you're doing. You can even use the Vivoactive on an ultramarathon by Charge On The Run, something that much harder with the M400. Both watches will support the Stryd Footpod for extremely accurate distance and pace information, but they have different trade-offs. The M400 can still record a GPS track whilst getting distance and pace from the Stryd, where the Vivoactive has to have GPS disabled. On the other hand, the Vivoactive can display the Stryd estimate of Running Power far better than the M400, and it can record this power estimate along with other metrics such as Ground Contact Time. Therefore, I'd only recommend someone buys the M 400 if they really want to record the GPS track whilst getting pace and distance from a Stryd Footpod, otherwise by the Garmin Vivoactive.

2 Polar M400 Pros

The user interface is nicely designed and intuitive; the buttons, display, and the menu system combine aesthetics with usability. The M400 has five hard buttons, which I much prefer over a touchscreen interface, especially when wearing gloves or in the rain.

The support for Stryd is pretty good. As noted above, you can get pace and distance information from the Stryd whilst still recording a GPS track. The Limited navigation features mean that the GPS data is of limited use while you're running, but it does allow you to see where you went afterwards. You can only get the Stryd estimate of power through the cadence field, and that feature might disappear in the future.

Like the Suunto Ambit2 and Polar V800, the M400 can be configured via the website, which is easier than fiddling with the watch itself. Most of the options can be also set on the watch, which means you're not stuck if you're away from the Internet.

The M400 provides more information when you press the lap button than most other watches.

The M400 can act as a simple activity monitor, but it only has only an internal accelerometer which provides poor accuracy.

The cable to charge and sync the M400 is a standard micro-USB that's waterproof. Most watches use a specialist cable that's expensive to replace if lost.

3 Polar M400 Cons

Polar has added support for a Footpod with version 1.4 of firmware, but this is problematic.

The Polar Stride Sensor is fully supported by the M400, with automatic calibration and it will display stride length as well as cadence. However, the Stride Sensor is huge and heavy when compared with modern Footpods, weighing over three times as much as a Garmin Footpod. Because of its size and weight, it requires lacing into the shoelaces, making it a real pain to move between shoes.

Some third party Bluetooth Footpods, like the "i-gotU" will pair with the M400, but then won't display cadence and prevent the M400 from recording any distance travelled.

The Adidas miCoach Speed Cell will work with the M400, but it's not easy. By default it will pair with the M400, but you can't set the calibration factor nor can you set the M400 to use GPS for pace/distance. You have to pair the M400 with the Polar Speed Sensor to activate the menu items you need to configure the Adidas Footpod, which is far from ideal. However, the Adidas Footpod is then a reasonable size and provides cadence (though not stride length). .

The M400 claims to have more rapid initial satellite acquisition than earlier watches, but I have not found this to be the case.

In my testing, I found "Time To First Fix" (TTFF) on the M400 is comparable or slightly slower than the older Garmin 610. (I tested after a 4+ hour gap since the last fix as most devices will reacquire rapidly if the gap is shorter.)

Polar states they use AssistNow, a technology from u-blox which does satellite prediction. AssistNow can use a downloaded prediction file or simply calculate the positions offline. With version 1.4 of the firmware, the synchronization software was updated to indicate that the offline file had been downloaded, and the watch will now indicate how long the file is valid for. However, even with version 1.4, the TTFF is still slow compared with competing devices.

Like the Polar V800, the M400 uses visual tricks to appear smaller than it is. The watch is curved, so the first part of the watch strap is really part of the watch body. This can cause problems for runners with smaller or larger wrists. I have to wear the V800 and M400 over a wrist sweat band as my writs are quite small. (I have no problem with watches that appear to be bigger, like the Garmin 310XT.)

There is no vibration alert, something I miss.

I've found the battery on the M400 seems to run low far earlier than the claimed 8 hours. I've had the low battery alert after only 4 hours, though I was using the backlight. I've also found that leaving the M400 in the state where it is ready to start, with the GPS signal acquired, the battery will run down quite quickly. Slower marathon runners could have problems with the battery life of the M400, and it could not be used for most ultramarathons.

The M400 will give an estimate of V̇O2max if you're wearing a Heart Rate Monitor, but I didn't find its estimate as accurate as the Firstbeat software used by Garmin and Suunto.

It's a minor problem, but if you have a Heart Rate Monitor strap paired with the M400 but don't have it on you, the M400 will wildly overestimate your calories and effort.

4 What's Missing

While I don't consider these missing features as 'cons', it's worth understanding the features that are missing compared with other watches.

Altimeter. GPS is far less accurate vertically than horizontally, so a barometric altimeter can provide a much better idea of your ascent and descent. It can also be useful for navigation if you're ascending or descending a mountain. In some races I've been far more interested in how much ascent is left rather than the distance to the top.

Navigation. The navigation capabilities are useful if there is a risk of getting lost. I've made good use of this feature when running in an unfamiliar city, or when running remote trails. There is a rudimentary "back to start" functionality that gives you an arrow pointing back, but that's a poor substitute.

Downloadable Apps. Smart watches have got is used to the idea of a device that can be extended with new functionality, and this concept is being introduced to running watches.

Extended battery life. Some porches can extend the battery life by turning the GPS reception off for short periods. This can dramatically reduce GPS accuracy, but it's a useful trade-off for some ultramarathons.

Training Effect. The Firstbeat Training Effect gives you a sense of how hard each workout is, and this sometimes includes the time for recovery.

Graphs. Instead of simply displaying a numeric value for things like heart rate, some watches will display a graph of the value over time, giving you a sense of how things are progressing.

Running Dynamics. Some of the newer Garmin watches can show and record Vertical Oscillation (VO) and Ground Contact Time (GCT).

Alerts. Some watches will alert you when a metric is out of range. The alert for Cadence is really useful and one of my favorite features. (Of course the M400 doesn't even support Cadence.)

WiFi/Bluetooth Uploads. While the automatic upload of workouts via WiFi or Bluetooth to a Smartphone is nice, the upload will typically only go to the manufacturer's web site.

5 GPS Accuracy

For quite some time, the M400 had the worst GPS accuracy of any device I've tested, but recent firmware upgrades have improved matters somewhat. The GPS accuracy is still rather mediocre at best, but at least it's not as appalling as it once was. It looks like Polar are using an unusual GPS chipset in the M400. I've not seen any other device using the u-blox chipset, and the replacement for the M400 (M430) returns to using the same chipset manufacturer as the Polar V800 which has outstanding GPS accuracy. The firmware upgrade is also fixed the problem where the M400 would report losing satellite signal with the message "There's no GPS signal". This was occurring under conditions where another device is doing fine and there are not circumstances that should cause a problem

Here's the tracks from the M400 with the 1.9 firmware. This diagram has tracks color coded with green indicating good accuracy through to red indicating poor accuracy, and the lap markers as blue dots.

For comparison, this is the M400 with the earlier 1.4 firmware. You can see a few tracks where the M400 has shifted out of position even though the shape of the course is maintained. The blue lap markers are quite spread out, suggesting some positional accuracy problems. You can see from the green lines going under the bridge that the M400 does quite well in that situation, and there are no sudden changes in position on emerging. I suspect this is because the M400 is doing a lot of smoothing, which works well in that situation. The middle segment that is quite curved is nearly all red, and this is one of the areas where the M400 is a smoothing too much and cutting the corners. You can see the M400 does worse here than in the sharp turn to the right of the image.

The Polar V800 is one of the most accurate devices I've tested, and you can see that the majority of the tracks are green indicating good accuracy. Notice the problems the V800 is having at the bridge. Rather strangely the lap markers are far more spread out than I would have expected on a device this accurate.

6 Visual Comparison

Polar M400 top

Polar M400 side

Polar V800 top

Polar V800 side

Suunto Ambit3 top

Suunto Ambit3 side

Suunto Ambit2 top

Suunto Ambit2 side

TomTom Cardio Runner top

TomTom Cardio Runner side

Garmin Epix top

Garmin Epix side

Garmin 920XT top

Garmin 920XT side

Garmin 620 top

Garmin 620 side

Leikr 1 top

Leikr 1 side

7 Comparison Table

I evaluate running watches in three distinct ways. Firstly, you can use a watch on its own, without any kind of Footpod. This is probably the most common way runners use their watch, but you miss out on a lot. The second rating is with a standard Footpod that is available quite cheaply. These Footpod's can be reasonably accurate once the calibrated, but calibration is a little tedious. The final evaluation is with the Stryd Footpod, which is vastly more accurate than any other type of Footpod, or and more accurate than GPS. The table below looks at the score, and the value for money of each watch for each of the three conditions. (I’ve also tested the Apple Watch 3, but I’ve not included it in these tables as it’s not really a running watch.)

The score is the sum of how well each watch can answer the four basic questions (how far, how fast, where are you, what's your cadence), plus some bonus points.

The "How far you've run" will be based on GPS only for "without Footpod" and "with Standard Footpod", but based on Stryd if supported in the "with Stryd Footpod" table..

How fast you're running assumes you're using a Footpod if it's supported, otherwise the rating is 0-2 based on GPS accuracy.

The "Where are you?" is based on various navigation features such as back to start, breadcrumbs, and preloaded maps. For some watches, you have to turn GPS off to get the benefit of Stryd, so those watches have worse "where are you scores" with Stryd than without.

The cadence score uses 1 point for an internal cadence sensor, 2 points for footpod support, 1 point for support from chest strap cadence, and 1 point for cadence alerts.

Value for money is the score divided by the price (at the time I last updated the table.) Your needs may be different, so you might weight the different aspects of the watches differently, or be basing your decision on different criteria totally. Hopefully this table will give you a good starting point for your decision.